you get scroll bars only when you set the child widgets in it,. No child widget means, you don't need/ get any scroll bars.
By default, the scroll bars are displayed only when the viewport is smaller than the child widget. You can force the scroll bars to always be shown by setting scroll bar policies.

I created a scroll area in Designer and moved all the widget into the scroll area. I see the widgets, and there are scroll bars on the side but they are inactive. How can I set the view area in a way, that when some of the widgets are off the screen the scrollbars show and work?
Thank you.